Add temporary way to configure amount of data prefetched per file han… #609

Job	Run time
Benchmarks / Benchmark (Throughput)	1h 40m 12s
Benchmarks / Benchmark (Cache)	1h 47m 6s
Benchmarks / Benchmark (Latency)	6m 49s
Benchmarks (s3express) / Benchmark (Throughput)	1h 39m 17s
Benchmarks (s3express) / Benchmark (Latency)	6m 47s
	5h 20m 11s

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